Alert Notice 445 - Request for monitoring of SS Cygni in support of European VLBI radio observations

August 19, 2011: Following their very successful multiwavelength observing campaign on the dwarf nova SS Cygni in 2010 April (see AAVSO Special Notices #204 and 206 and the related information page), Dr. James Miller-Jones (International Centre for Radio Astronomy Research, Curtin University, Perth, Western Australia) and colleagues have a follow-up multiwavelength campaign on SS Cyg scheduled. As before, they are requesting the assistance of AAVSO.

THE FIRST POTENTIAL OBSERVATION DATE IS AUGUST 25-26, 2011.

Dr. Miller-Jones writes, “To bring you up to speed with our main results, we found marginally-significant evidence for a resolved radio jet following the outburst, and the highly-accurate positional information we obtained from our VLBA campaign implied that the currently accepted distance and proper motion for the source (derived from HST observations) cannot both be correct, although we do not yet have sufficient radio data to determine the true parameters. We therefore requested (and were awarded) follow-up observations with the European VLBI Network to rigorously constrain the distance and proper motion. There is approximately one day per month when we will be able to trigger the EVN. These are:

- 2011 August 25-26

- 2011 September 6-7

- 2011 October 17-18

- 2011 November 23-24

- 2011 December 14-15

The possible trigger dates will continue through 2012, although the exact dates are not known yet for next year. Ideally we would like to know the state of SS Cyg (particularly whether or not it is going into outburst) a few days before each of these dates, to give us time to alert the schedulers and get on the telescope if appropriate. We would be extremely grateful for any assistance the AAVSO could provide.”

SS Cyg is the class prototype of the dwarf novae, and the brightest dwarf nova in our skies. In quiescence, SS Cyg varies around V=12.0, and will typically reach V=8.0 at maximum, although anomalous weak outbursts are sometimes seen. SS Cyg last went into outburst 2011 June 26 (JD 2455738.75171, 11.49 V, R. James; 2455739.4201, 10.9, M. Bisson); the outburst was a wide one, lasting 20 days. The next outburst may occur at any time. Observations brighter than m(vis) = 11.0 should be reported as quickly as possible.

Observers are asked to increase their monitoring of SS Cyg at least through December. Please report all observations as soon as is practical. In the event of an outburst, please report your observations as quickly as you can via WebObs, and also notify Dr. Matthew Templeton and Elizabeth Waagen at AAVSO Headquarters (matthewt@aavso.org, eowaagen@aavso.org). Visual magnitude estimates are a fast and effective means of monitoring SS Cyg; CCD observations are also useful, but please reduce your frames and report your data as soon as possible following an observing run. CCD time-series are not specifically required for this project.